Provided is a method of preparing an SnSe thermoelectric material including (a) heating a mixture including Sn.sup.2+ and Se.sup.2−, (b) cooling the mixture at a cooling rate greater than 0 and equal to or less than 3 K/h, and forming single crystal Sn.sub.1−xSe (where 0<x<1), and an SnSe thermoelectric material prepared thereby and including Sn vacancies.

Embodiments relate to a layered material (having a substrate, at least a buffer layer, with zero or more growth layers) that has been intercalated via a process that decouples (physically and electronically) the buffer layer from the substrate, thereby resulting in the creation of few-atom thick metal layers that exhibit a range of optical properties, including plasmonic or electronic resonance, that enables superior optical (e.g. Raman) detection of molecules.

Embodiments relate to a layered material (having a substrate, at least a buffer layer, with zero or more growth layers) that has been intercalated via a process that decouples (physically and electronically) the buffer layer from the substrate, thereby resulting in the creation of few-atom thick metal layers that exhibit a range of optical properties, including plasmonic or electronic resonance, that enables superior optical (e.g. Raman) detection of molecules.

Embodiments of this disclosure include apparatus, systems, and methods for fabricating monolayers. In one example, a method includes forming a multilayer film having a plurality of monolayers of a two-dimensional (2D) material on a growth substrate. The multilayer film has a first side proximate the growth substrate and a second side opposite the first side.

A process for epitaxying GaSe on a [111]-oriented silicon substrate, includes a step of selecting a [111]-oriented silicon substrate resulting from cutting a silicon bar in a miscut direction which is one of the three [11-2] crystallographic directions, the miscut angle (α) being smaller than or equal to 0.1°, the obtained surface of the substrate forming a vicinal surface exhibiting a plurality of terraces and at least one step between two terraces; a passivation step consisting of depositing an atomic bilayer of gallium and of selenium on the vicinal surface of the silicon substrate so as to form a passivated vicinal surface made of silicon-gallium-selenium (Si—Ga—Se), said passivated vicinal surface exhibiting a plurality of passivated terraces and at least one passivated step between two passivated terraces; a step of forming a layer of two-dimensional GaSe by epitaxy on the passivated surface, said formation step comprising a step of nucleation from each passivated step and a step of lateral growth on the passivated terraces from the nuclei obtained in the nucleation step. A structure obtained by means of the epitaxying process is also provided.

A process for epitaxying GaSe on a [111]-oriented silicon substrate, includes a step of selecting a [111]-oriented silicon substrate resulting from cutting a silicon bar in a miscut direction which is one of the three [11-2] crystallographic directions, the miscut angle (α) being smaller than or equal to 0.1°, the obtained surface of the substrate forming a vicinal surface exhibiting a plurality of terraces and at least one step between two terraces; a passivation step consisting of depositing an atomic bilayer of gallium and of selenium on the vicinal surface of the silicon substrate so as to form a passivated vicinal surface made of silicon-gallium-selenium (Si—Ga—Se), said passivated vicinal surface exhibiting a plurality of passivated terraces and at least one passivated step between two passivated terraces; a step of forming a layer of two-dimensional GaSe by epitaxy on the passivated surface, said formation step comprising a step of nucleation from each passivated step and a step of lateral growth on the passivated terraces from the nuclei obtained in the nucleation step. A structure obtained by means of the epitaxying process is also provided.

Disclosed herein is a method for 2D epitaxial growth comprising: forming a single crystalline h-BN template; forming a plurality of nuclei by depositing a heterogeneous precursor on the h-BN template; and forming a heterogeneous structure layer by growing the plurality of deposited nuclei with a van der Waals epitaxial growth, wherein the heterogeneous structure layer is a single crystal.

Disclosed herein is a method for 2D epitaxial growth comprising: forming a single crystalline h-BN template; forming a plurality of nuclei by depositing a heterogeneous precursor on the h-BN template; and forming a heterogeneous structure layer by growing the plurality of deposited nuclei with a van der Waals epitaxial growth, wherein the heterogeneous structure layer is a single crystal.

The present invention discloses a method for preparing large-area transition metal dichalcogenide (TMDC) single-crystal films and the products obtained therefrom. The method comprises the steps of: (1) providing a single-crystal C-plane sapphire with surface steps along <1010> directions; and (2) taking the sapphire in step (1) as the substrate, generating unidirectionally arranged TMDC domains on the sapphire surface based on a vapor deposition method and keeping the domains continuously grow and merge into a large-area single-crystal film. The lateral size of the TMDC single-crystal films prepared by the method can reach inch level or above, and is limited only by the size of the substrate.

The present invention discloses a method for preparing large-area transition metal dichalcogenide (TMDC) single-crystal films and the products obtained therefrom. The method comprises the steps of: (1) providing a single-crystal C-plane sapphire with surface steps along <1010> directions; and (2) taking the sapphire in step (1) as the substrate, generating unidirectionally arranged TMDC domains on the sapphire surface based on a vapor deposition method and keeping the domains continuously grow and merge into a large-area single-crystal film. The lateral size of the TMDC single-crystal films prepared by the method can reach inch level or above, and is limited only by the size of the substrate.